I just recently discovered that my 4104 radiator shutters work fine. Most of the almost one year I've owned it I thought the shutters were rusted open because it never ran higher than 140-150 on flat ground. It ran 130 on cold days in April in the Rockies. Sometimes it would go as high as 180-190 on long grades but go right back down to 130-140 downhill.

I just finished a 1300 mile trip in mostly 95+ degree/100+ % humidity and they worked perfectly. The heat gage stayed between 178 and 188 depending of the conditions. Yesterday, one of our hottest so far, it stayed right on 178 for about 400 miles. I guessed that the shutters were completely open all this time because the other three days the temp fluctuated between 182 - 188 and 185-192, it was never completely stable at any one temp.

Call me a bit weird but I get a kick out of seeing these ancient systems work just as advertised.

They didn't work before because the drain valve at the shutter air valve leaked and the air had been turned off!!

gusc: The radiator shutters are not there to control the engine temperature. They open when the temperature goes above the shutterstat set point. Your engine should never be run at 130*. If your temperature gauge is working properly, the engine thermostat must be stuck open or someone has removed it. You can test the gauge by putting the sender in water and heating the water. Be sure to connect the sender body to ground. If the gauge is correct, then pull the themostat and if it is stuck open, jist replace it with the recommended temperature (180* - 185*)

Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming: WOO HOO, what a ride

I always thought they were to close in cold weather to reduce the air flow across the radiator and allow the engine to warm up or to keep it warm, thereby controlling the engine temperatrure, but what do I know? LOLRichard

Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming: WOO HOO, what a ride

Richard: Like you I am writing from memory (not good) but I think the DD manual give specific temperature spreads for the thermostat, fan and finally the shutters. The shutters are not to control the emgine temperature, that is the function of the thermostat. The shutters prevent engine overheating when the thermostat is wide open and thee is not enough cooling in the radiator without more airflow.

I expect that the shutters do stop some cold air cooling of the engine during warm up, but thrucks with thermostatic fans also use shutters so there is no forced air circulation until the fan cuts in at almost wide open thermostat. IIRC there is some overlap of the temperature controllers so that the fan cuts in before the the themostat is wide open. On a MCI bus with a constant fan, the dampers should open and allow air flow over the engine before the shutters open. HTH

I heard the shutters are there when the bus was a bus and carried lots of people.When the interior heaters were on full the engine would drop in temp with the rads and inside heat.So the shutters would close and block off the rads, all available heat to the people.The engine thermostats control the engine temp.I have an AquaHot for interior heat so I removed the shutters for MORE air flow to the rads.Frank

Frank: A local bus company doing construction crew transportation had complaintsd of cold feet in their 4104's in -40* weather. They installed Webasto heaters for supplemental heat. In buses with a 8V71 engine they put spray foam on the underside of the floor and that was suffiicient to stop the union complaints. I bought a MC-5 from this company with the sprayed in foam and wondered how a worker dressed to work outside was too cold inside a heated bus. You are correct that in very cold weather the heater core can cool down a 6-71 engine.

I am suprised nobody noticed the error in my previous post. The temperature contol sequence is thermostat, shutters and then fan. On a truck, the fan only comes on when ram air through the rad is not sufficient.

gusc: I re-read your original post and I think you still have a temperature control problem. Running hard on a very hot day will have the engine thermostat wide open and the radiator shutters open. Iif you are lucky, and have a good clean cooling system, the temperature will stay in the 180* range under those conditions. This means that you are at the maximum capacity of your cooling system.

If you have not changed anything except turn on the air to the shutter control, your engine will not come up to the proper operating temperature on a cooler day. That is the way I understand your first post, and I think you have an engine thermostat problem.

When the engine thermostat is closed, water dosen't circulate through the radiator and a working engine transfesr a lot of heat into the water in the block. If the thermostat stays closed, the water will boil. If it opens (as a good thermostat will) the water starts to circulate through the radiator before it reaches the thermostat set point. If the thermostat is set for 180* it will start to open about 170* and when the temperature reaches 180* it will modulate to hold it at 180*. Overheating occurs when it is wide open and the temperature continues to rise in the engine and the radiiator does not provide sufficient cooling to the circulating water. HTH If it is clear as mud to you, ask more questions and I will try and help.

If temp is stabilized at 180 deg (180 deg Thermostat) and all else being equal and properly maintained, there still is more capacity in the system as it should allow for a certain amount of coolant aeration and the need to cope with the potential for a certain amount of exhaust gases leaking into the cooling system. The fact that sustained temps at 195* or the planned shutdown of 205* means there is more capacity in the system. But just because it's there doesn't mean that it's a good idea to venture in to these areas of the perfomance envelope.

Second, if the thermostat is closed, the bypass hose provides for a minimal, but necessary, circulation of water within the block. Otherwise, if the water circulation was stopped, it could get real hot at the cylinder heads and the thermostat would never ( or much too late) find out about it.

These points are anecdotal and don't change Stan's post in any significant regard. The relationship between the shutters and maintaining coolant temp secondary to maintaining engine temp could be restated in a more together or cogent fashion.

These points are anecdotal and don't change Stan's post in any significant regard. The relationship between the shutters and maintaining coolant temp secondary to maintaining engine temp could be restated in a more together or cogent fashion.

Logged

Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming: WOO HOO, what a ride

Richard: Different methods have been used to control the low temperature. The engine thermostat does a fairly good job of bringing the engine up to operating temperature quickly if there is suffiecient load on the engine. Probably the ideal way is to preheat the engine coolant to 180* before starting. This is easily done with a propane fired engine coolant heater or a Webasto type heater.

If you want to maintain some fixed amount or temperature spread between the top and bottom of the engine, when running, then you need a pretty exotic controller. Our older model buses were built when industriial pneumatic temperature controllers were common but the price and complexity of the system was prohibitive. With microprocessors on a DDEC style engine it is more feasible.

Many of the older engines used a primitive form of delta T control by using variable pitch fans, fluid drive fans and on-off fan control. They all had the same limitation in that they were operated by an on-off temperature sense switch which could not anticipate a change or determine the rate of change, or indeed even the amount of change. A convential shutterstat only switches when the temperature is either above or below the setpoint which means it will never stop at the setpoint, which is what you want.

With micropreocessor control you can measure the water temperature at the top and bottom of the engine and adjust the fan speed and shutter opening to maintain any desired spread.

All of this is academic with the buses that were built with DD 2-stroke engines as they all had either a marginal or inadequate cooling system when they were built. I doubt if any bus operator ever asked the factory to increase the water temperature returning to the engine.

Marc: Engine designers make an educated guess at how hot you can run an engine without doing major damge. They then recommend that the engine be operated somewhat below that temperature. That does not change the fact that you have exceeded the capacity of the cooling system when you can no longer maintain the setpoint temperature. Running it hotter than that just gets you closer to the potential damage temperature.

If you read the first post by gusc, I think you will agree that he had a non functioning thermostat and I directed my reply to him since itt appeared that he didn't understand the 'basic' operation of the cooling system.

Stan, AFAICR, you've shown greater understanding of cooling systems as any non-pro that's appeared on the BB boards.

Talks with Bob Sheaves leads me to believe that engineers make more than educated guesses. In the 80's they'd instrument an engine to the cost of hundreds of thousands of dollars. Today's new designs spend much more than that. Bob Sheaves is currently on contract with Freightliner upgrading cooling systems. The cost for the "upgraded" cooling system for the Austrailian trucks, used to pull trailer "trains" across the Outback, is considerably higher. Bob touched upon this activity during the "All you NEVER wanted to know about cooling systems and were afraid to ask" seminar I more or less moderated at Bus'nUSA last weekend.

AFAIK. there isn't a particular "setpoint temperature" due to a host of variables, what a cooling system engineer seeks/uses, instead of a "setpoint temperature" is the temperature at which the cooling system reaches equilibrium. If that stablized temp is below the max acceptable engine mfg temp ( maybe your definition of setpoint??) it's within limits. Otherwise, they have to increase capacity.